Typically, electric fans, such as of the portable or ceiling fan variety, have been employed to circulate air in an environment through the movement or rotation of the fan blades by an electrical motor so as to permit the movement of the air by the rotation of the angle fan blades of the fan. The prior art, of course, is replete with pneumatic devices which serve to establish currents of air for various purposes. Among such devices are those employed for purposes of enhancing the comfort of occupants of an enclosure, such as the room of a dwelling or similar enclosure. These devices frequently are referred to as fans and include impellers which serve to establish cooling currents of air as rotation is imparted thereto. In some instances, a fan is designed to operate in close proximity with a floor in order to cause streams of air found in cooler zones, just above the level of the floor, to move upwardly into the air of warmer zones for cooling purposes. A fan of this type which has experienced generally widespread acceptance often is referred to as a Hassick fan. Such a fan frequently is adapted to be seated on the floor and is provided with impeller blades which serve to impart vertical momentum to a body of air, whereby an upwardly directed air current is established as rotary motion is imparted to the blades. Of course, as can be appreciated by those who are familiar with such fans, the efficiency often is less than desired, simply because the currents thus established lack sufficient horizontal momentum and velocity to perform a suitable cooling function.
Another type of fan sometimes employed for purposes of circulating air within a room includes an impeller having blades supported for rotation about a horizontally extended axis for purposes of establishing a horizontally directed stream of air. Such fans, also, have acquired general acceptance. However, as can be appreciated by those familiar with these devices, the air streams established through an operation thereof tend to be highly directional. Unfortunately, such devices are, in many instances, found to be impractical due to their innate directional characteristics and the attendant turbulence created through an operation thereof.
Centrifugal fans also are well known. These fans are characterized by impellers having arrays of elongated blades supported in substantial parallelism. Frequently, the impellers of centrifugal fans are employed in the substantially closed housing for accelerating streams of air through a conduit, while the conduit and housing serve to convert the velocity of the air to pressure. Such impellers, generally, are not employed without an housing and tend to lack a capability for establishing suitable air currents in open spaces such as are needed in the cooling of rooms of a dwelling.
Since fans adapted to circulate room air for cooling occupants generally have experienced widespread acceptance, and the use thereof is highly desirable, particularly in those instances where refrigerated air is not available, attempts to increase the overall efficiency of such devices is sought continuously.